1. Field of the Invention
The present invention relates to a BGA (Ball Grid Arrays) package using a dummy ball and a repairing method thereof capable of performing a local repairing of a solder joint.
2. Description of the Prior Art
Referring to FIG. 1, in a conventional BGA package, a predetermined thickness of solder resist film 9 is bonded at a front and rear surface of a substrate 1. A semiconductor chip 3 is bonded at a central part of the substrate 1 by using an adhesive (not shown), and penetration holes 8 are formed at a predetermined portion of the substrate 1. Conductive patterns 5 are formed in each of the penetration holes 8 in the substrate for an electrical connection between the upper and lower portions thereof. Wires 4 are connected at one end thereof to an upper surface 5a of the conductive patterns 5 and at their other ends to pads 3a of the semiconductor chip 3. A plurality of solder balls 6 are formed at a predetermined portion of a lower surface 5b of the respective conductive patterns 5.
After the wires 4 are connected, the BGA package is molded by an EMC (Epoxy Molding Compound) 7, and the plurality of solder balls 6 are arranged at regular intervals at the lower surface of the substrate 1 and are reflowed so as to be mounted.
FIG. 2 is a cross-sectional view of a conventional BGA package mounted to a printed circuit board (PCB).
First, in order to mount the BGA package on the printed circuit board, the BGA package as shown in FIG. 1 is aligned on the printed circuit board 10 and reflowed so that the solder balls 6 of the BGA package are electrically connected to pads 10a formed on the printed circuit board 10.
However, the BGA package manufactured by the steps described above wholly depends upon the soldering step in view of its reliability. In the meantime, when a defect is found in an electrical testing, it requires a method which removes the entire BGA package under the condition that its temperature is raised, resulting in a disadvantage in that repairs are not easy.
In addition, in the BGA package, in case that the solder balls are not properly connected to the printed circuit board, highly increased impedance value appears in an external electrical testing. In this case, in spite of a partial inferiority of the solder balls, the BGA package should be removed after all of the solder balls are melted, and then, a cleaning step is performed, and thereafter a new BGA package is mounted, so that the overall process becomes complicated.